Kyle Stanley and Spencer Levin, who are both seeking their first USPGA Tour wins, seized a share of the lead after the opening round of the $6 million Farmers Insurance Open.
Levin shot a 29 on the back nine of the North Course at Torrey Pines and Stanley holed an eagle on 18 as both fired 10-under 62s on Thursday.
"I played the pro-am on the North Course yesterday. There were just a lot of birdie opportunities out there so I knew there was a good score -- maybe not 10 (under), but I'll take it," Stanley said.
Levin added: "Maybe that?s why I shot that because I just kept trying to hit every shot as good as I could, and I just had a good rhythm going.
"My mind was pretty clear and it just worked out good. I played really well on that back nine."
The duo are a stroke in front of fellow American Bill Haas, who made double bogey on his 15th hole but battled back to finish with a nine-under 63.
Marc Turnesa had the lowest score on the South Course -- considered more difficult than the North -- by firing a 66.
Three-time champion Phil Mickelson struggled mightily as he finished with a 77. Mickelson missed a short birdie putt on the final hole and found 11 bunkers in his round.
"Obviously I had some bad swings just in the wrong spots and so forth," Mickelson said. "But I felt like my game was ready heading in and I don?t know what to say about the score because it was pathetic."
Fiji's Vijay Singh, Rod Pampling, Josh Teater and John Huh were at 64. Huh had three eagles. Camilo Villegas and Aussie Greg Chalmers were in a group at 65.